1. Technical Field
The present invention relates to a driver apparatus that drives and moves a moveable unit in a given path, and an image forming apparatus including the driver apparatus.
2. Background Art
In image forming apparatuses using the inkjet method, a moveable unit such as a carriage includes a recording head having nozzles to dispense ink droplets. Further, a driver apparatus including a drive unit such as a main scanning motor (or scanning motor) for driving and moving the carriage along an axis is disposed in the apparatuses. The axis is set along the main scanning direction which is perpendicular to the sub-scanning direction that is a transportation direction of a recording medium.
In such image forming apparatuses using the inkjet method, while the carriage is driven and moved bi-directionally along the axis using the main scanning motor, ink droplets are dispensed from nozzles of the carriage at a given timing of forming an image on a recording medium based on image data. The control of moving the carriage bi-directionally in the main scanning direction may be referred to as carriage control in the main scanning direction. In the image forming apparatuses that conducts the carriage control in the main scanning direction, a position of the carriage in the apparatuses needs to be detected correctly to form an image on a target position on a recording medium. An encoder is attached to the carriage and a linear scale is disposed in parallel to the main scanning direction in the apparatuses to detect the carriage position.
In such image forming apparatuses, a controller conducts the following feedback control to drive the carriage. In this feedback control, the controller instructs the encoder to read the linear scale when the carriage is moved along the main scanning direction. Based on encoder signals output from the encoder such as an encoder sensor, the carriage position is detected, and position information of the carriage is obtained. Then, based on the position information of the carriage, an output such as voltage to be supplied to the main scanning motor is determined Based on the determined output, driving of the main scanning motor is controlled, with which speed and position control of the carriage are conducted. In such image forming apparatuses having the feedback control, upon detecting no input of encoder signal when the encoder conducts reading of the linear scale (i.e., input error), it is determined that abnormality occurs, and the carriage is stopped.